Fri, 10pm, Law & Order: SVU, Five
Tonight’s episode is more tense than usual, as the detectives’ usual means of crime-solving doesn’t work. They’re faced with a spate of murders around New York City, which appear to be the work of a serial killer  called RDK (I’ll leave it to the show to explain the rather grisly background to that catchy nickname) who hasn’t struck for 20 years, and he’s deliberately taunting them with riddles and puzzles. There’s just one thing niggling away at the cops as they chase all over the city - is this really RDK or is it a copycat killer?

Sun, 9pm, NCIS, FX
Another mass murderer, another possible copycat killer at work. Former Mossad agent Ziva goes undercover to try to trap a serial killer, a perilous job that requires all her training to deal with. The problem is that it seems there may well be another murderer on the loose who has managed to stay under the radar until now, so the team really have their work cut out for them.

Sun, 10pm, Dexter, FX
Dexter tries to distance himself from Lila - but funnily enough she’s not that easy to get rid of. Speaking of people who don’t know when to let things lie, Doakes’ dogged pursuit of Dexter finally reaps a reward, and he has the evidence he needs to nail Dexter once and for all. Somehow you know it’s not going to be that simple - but how on earth is Dexter going to get out of this one? (I seem to find myself thinking this in every single episode!)